The invention relates to ear seals for use in noise attenuating headsets and other like headgear incorporating ear protectors designed to reduce noise levels.
Circumaural hearing protectors function by enclosing the ears of a user within earcups, typically plastic domes. Conformable ear seals are interposed between the earcups and the user's head to assist in isolating the ears from offending noise originating outside the earcups. The earcups are typically attached to a spring and suspension assembly which applies a force urging the ear seals in place against the head of the user.
Various problems exist which limit the effectiveness of circumaural hearing protectors. The noise attenuation achievable by hearing protectors at low frequencies is extremely limited due to undesirable vibration of the dome and ear seal assemblies induced by external noise. Also, leakage occurring between the head of the user and the ear seals provides a direct path for the entry of external noise. At lower frequencies below about 1 kHz, bone conduction of vibrations further limits achievable noise attenuation. In addition, vibrations may be transmitted along the surface of the flesh of the user under the ear seals so as to penetrate the earcup.
The prior art includes ear seals which attempt to address the above mentioned problems in hearing protectors. For example, Lundin U.S. Pat. No. 4,674,134, entitled "Ear Muff Having Sealing Ring Including Liquid and Foam Plastic Layers", describes a sealing ring having a liquid layer enclosed in a sheath overlying a foamed plastic layer. The ear seal includes an inner sheath which encloses the liquid layer, and an outer sheath which encloses both the inner sheath with the liquid layer and the foamed plastic layer. Sapiejewski U.S. Pat. No. 4,856,118, entitled "Head Phone Cushioning", describes a head phone cushion having two concentric rings of non-liquid silicone gel on a layer of soft, slow recovery foam enclosed in a thin stretchable layer of polyurethane skin.
Noise attenuation and comfort are qualities which are normally in conflict with one another in circumaural hearing protector systems. High attenuation has typically dictated the use of stiff, non-springy ear seal materials which because of their nonconforming nature, require excessive head band clamping force to insure a good acoustic seal against the head of the user. The result is often an ear seal that provides good attenuation at the expense of user comfort.
Soft ear seals with larger geometry and low head band clamping force provide comfort to the user, but allow the transmission of vibrations, reduced damping, and lower attenuation. The low clamping force increases the likelihood of leaks at the interface between the ear seal and the head of the user.
It is therefore an object of the present invention to provide an ear seal that offers superior attenuation as well as a high degree of comfort.